/*
 * jPOS Project [http://jpos.org]
 * Copyright (C) 2000-2015 Alejandro P. Revilla
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as
 * published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

package org.jpos.q2.qbean;

import org.jpos.q2.QBeanSupport;

import java.io.File;
import java.io.FileOutputStream;
import java.io.RandomAccessFile;
import java.nio.channels.FileChannel;
import java.nio.channels.FileLock;

public class QSingleInstanceFileBasedManager extends QBeanSupport {

	File lockFile;
	FileChannel lockChannel;
	FileLock lock;
	FileOutputStream lockFileOS;

	/*
	 * (non-Javadoc)
	 *
	 * @see org.jpos.q2.QBeanSupport#initService()
	 */
	@Override
	protected void initService() throws Exception {

		try {
			lockFile = new File("./" + getServer().getDeployDir(), "instance.lock");
			if (lockFile.exists()) {
				// Either an orphan lock or lock from another instance. Orphan
				// lock will get deleted, the latter will not get a lock on it.
				lockFile.delete();
			}
			lockFileOS = new FileOutputStream(lockFile);
			lockFileOS.close();
			lockChannel = new RandomAccessFile(lockFile, "rw").getChannel();
			lock = lockChannel.tryLock();
			if (lock == null) {
				throw new Exception("Unable to obtain lock");
			}
		} catch (Exception e) {
			getLog().error("An instance of Q2 is already running. Shutting this instance");
			if (lock != null) {
				lock.release();
			}
			if (lockChannel != null) {
				lockChannel.close();
			}
			if (lockFile != null) {
				lockFile.delete();
			}
			getServer().shutdown();
		}

	}

	@Override
	protected void stopService() throws Exception {

		lock.release();
		lockChannel.close();
		lockFile.delete();
	}

}
